Book Image

ROS Programming: Building Powerful Robots

By : Anil Mahtani, Aaron Martinez, Enrique Fernandez Perdomo, Luis Sánchez, Lentin Joseph
Book Image

ROS Programming: Building Powerful Robots

By: Anil Mahtani, Aaron Martinez, Enrique Fernandez Perdomo, Luis Sánchez, Lentin Joseph

Overview of this book

This learning path is designed to help you program and build your robots using open source ROS libraries and tools. We start with the installation and basic concepts, then continue with the more complex modules available in ROS, such as sensor and actuator integration (drivers), navigation and mapping (so you can create an autonomous mobile robot), manipulation, computer vision, perception in 3D with PCL, and more. We then discuss advanced concepts in robotics and how to program using ROS. You'll get a deep overview of the ROS framework, which will give you a clear idea of how ROS really works. During the course of the book, you will learn how to build models of complex robots, and simulate and interface the robot using the ROS MoveIt motion planning library and ROS navigation stacks. We'll go through great projects such as building a self-driving car, an autonomous mobile robot, and image recognition using deep learning and ROS. You can find beginner, intermediate, and expert ROS robotics applications inside! It includes content from the following Packt products: ? Effective Robotics Programming with ROS - Third Edition ? Mastering ROS for Robotics Programming ? ROS Robotics Projects
Table of Contents (37 chapters)
Title page
Copyright and Credits
Packt Upsell
Preface
Bibliography
Index

Converting IMU data into twist messages


If you are able to the visualization in Rviz, you are done with the interfacing. The next step is to convert IMU orientation into command velocity as ROS twist messages. For this, we have to create a ROS package and a Python script. You can get this package from chapter_5_codes/gesture_teleop; look for a script called gesture_teleop.py from the gesture_teleop/scripts folder.

If you want to create the package from scratch, here is the command:

$ catkin_create_pkg gesture_teleop rospy roscpp std_msgs sensor_msgs geometry_msgs

Now let's look at the explanation of gesture_teleop.py, which is performing the conversion from IMU orientation values to twist commands.

In this code, what we basically do is subscribe to the /imu_data topic and extract only the yaw and pitch values. When these values change in the positive or negative direction, a step value is added or subtracted from the linear and angular velocity variable. The resultant velocity is sent using...